1. Field of the Invention
The present invention relates to an image display apparatus having a liquid crystal panel and to an optical compensation device used with the liquid crystal panel.
2. Description of the Related Art
Examples of image display apparatuses having a liquid crystal panel have been available. The examples of image display apparatuses include liquid crystal projector apparatuses in which the liquid crystal panel is used as an optical modulator. Liquid crystal projector apparatuses are configured to project an image modulated with a liquid crystal panel onto a screen, and are widely used as equipment for enlarging and projecting presentation material at meetings or lectures.
Improvement in the image quality of projected images is being demanded for liquid crystal projector apparatuses. One of important factors defining the quality of projected images is contrast. Contrast is the ratio in luminance between the black display state and the white display state.
In liquid crystal projector apparatuses, it is effective to minimize the luminance of a black display as much as necessary in order to improve the contrast. In actuality, however, certain factors such as the structure or nature of a liquid crystal panel serving as an optical modulator, and the state of light entering the liquid crystal panel from an illumination system may cause light leakage even in the black display state.
In order to prevent such light leakage, techniques used for optical compensation of the liquid crystal panel have been proposed. For example, multilayered thin films are used (see, for example, Japanese Patent No. 3162210), or a birefringent plate is used (see, for example, Japanese Patent No. 3864929). Alternatively, a plurality of birefringent members composed of a positive uniaxial birefringent material are used (see, for example, Japanese Unexamined Patent Application Publication No. 2007-286609).